This plugin will allow you to attach a single file to multiple posts, but will also will allow you to detach any file.

• Support http://xparkmedia.com/plugins/file-un-attach/
• Languages http://xparkmedia.com/plugins/file-un-attach/#languages

1. 

   Screenshot Media menu

2. 

   Screenshot File detach

3. 

   Screenshot File attach

• Download the latest version of the plugin to your computer.
• With an FTP program,access your site's server.
• Upload the plugin folder to the /wp-content/plugins folder.
• In the WordPress administration panels, click on plugins from the menu on the left side.
• You should see the "File Un-Attach" plugin listed.
• To turn the plugin on, click "activate" on the bottom of the plugin name.

Tested on

• MySQL 5.1.26
• Apache 2.2.11
• Linux
• Explorer 8
• Safari 4.1
• Firefox 3.5
• Chrome 5.1
• Opera 9.6

1.0.5

• Fixed: WP 3.5 support.
• Improved: language file loading.
• Fixed: php notices.

1.0.2

• Fixed: ajax error.
• Fixed: gallery sort order.

1.0.1

• Fixed: Performance issue.

1.0.0

• Code clean up.
• Hooks added.
• Multisite support
• Fixed: PHP notices.
• Fixed: issue saving different post types.

0.6.5

• Code clean up.
• Added: 3.4.0 support
• Added: Spanish language translation.
• Added: Full support for get_post, get_children, wp_query.
• Fixed: typo

0.6.0

• Code clean up.
• Fixed: Attached files not being displayed in media library.
• Fixed: Attaching new file in media library will remove files already attached.

0.5.5

• Code clean up
• Attach search improved
• Custom post type support
• Support for WP 3.0+
• "fun_get_attachments" function added, thank you @sebmeric

0.5.1

• Removed attach/unattach button from media library

0.5.0

• Beta release

• http://xparkmedia.com/support/plugin/file-un-attach/